This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Binding of the estrogen receptor (ER) to hormone and the estrogen response element (ERE) initiates transcription of estrogen responsive genes. However, it has become clear that the ER does not act in isolation but requires the participation of numerous coregulatory proteins. We are interested in identifying novel coregulatory proteins that interact with the DNA-bound ER and in determining whether the ERE sequence alters the association of proteins with the ERE-bound receptor.